©1998 Green Mountain Energy Resources

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©1998 Green Mountain Energy Resources

Tom Snyder

©1998 Tom Snyder

Above: IRENEW's 1000 Watt PV array supplying electricity to the Blues Bus in a farmer's yard during RAGBRAI.

Tom Snyder

©1998 Tom Snyder

Above: IRENEW's 1000 Watt PV array supplying electricity to the Blues Bus in a farmer's yard during RAGBRAI.

AGBRAI (The Des Moines Register's Annual Great Bike Ride Across Iowa) is one of the biggest gatherings of bicyclists in the world. Each summer, thousands of bikers from across the USA and from foreign countries come together for the ride, and to enjoy blues music concerts along the route. The Iowa Renewable Energy Association (IRENEW) decided that this was a perfect event for displaying and using alternative energy. Our Solar Power Trailer was rolling proof of the power of the sun as it supplied all of the electricity for daily blues concerts for the entire seven days.

Bikes—Another Form of Alternative Energy

RAGBRAI started in 1972 with about 500 bikers traveling east across Iowa from the Missouri River to the Mississippi River. This bike ride was organized by two Des Moines Register writers. Covering about 500 miles (805 km) over seven days, the ride has grown to about 25,000 riders total, including 10,000 officially registered riders. This traveling circus (as some have called it) enjoys many things: good food, good ale, and excellent blues music. In the spring of 1998 we brought our own Alternative Energy Tour vehicle to this event— an old school bus with a stage on the top, and the Solar Power Trailer for electrical power. Different blues musicians from across Iowa used the stage as we traveled across the state.

Recycling 5,000 Watts of Surplus PVs

In the spring of 1996, my son David, Don Laughlin, and I traveled to Brookhaven National Laboratory in New York to dismantle a 5 KW PV array that had been donated to IRENEW. Most of the 116 panels were then transported back to Iowa by the Iowa National Guard. IRENEW is an educational non-profit organization, so these panels were to be used specifically for education and demonstration. We have now completed two projects with 48 of these PV panels: the Indian Creek

Nature Center in Cedar Rapids, Iowa (see HP63) and the Solar Power Trailer. Future projects scheduled for some of the remaining panels are two straw bale guest houses for the Prairiewoods Nature Center in Hiawatha, Iowa.

PV Power Trailer Construction

We started building the Solar Power Trailer using a seventeen foot (5 m) boat trailer as our base. This trailer needed new brakes, new tires, and a new brake master cylinder, among other things. After the basic running condition was improved, IRENEW members Dennis Pottratz, Don Laughlin, Kirk Boyd, Tim Reynolds, and Pat Mulligan installed the power system. The system included twenty-four PV panels, sixteen 6 volt Exide batteries, and an Exeltech 4000 watt sine wave inverter, as well as all controls, hardware, and wiring.

The weight of the sixteen batteries—over half a ton— required them to be mounted directly over the two axles and between the frame rails. This arrangement has proven to be very stable for highway travel. The trailer has traveled extensively across Illinois and Iowa with no problems. Tires have been replaced as needed, but no other major repairs or replacements have been necessary.

The eight main upright posts for mounting the PV panels were constructed out of two inch (51 mm) square tubing welded to the boat trailer. At about four and one half feet (1.4 m) from the ground, angle iron was welded horizontally between all uprights. The angle iron forms the support for the bottom three strings of modules. It also serves as a roller guide when they are pulled out and lowered for use. The top three groups of modules are raised after the bottom three are pulled out and lowered.

Below: The back of the trailer, showing batteries and the red weatherproof control center.

Right: The trailer with one third of the array set up for charging and the other two thirds in travel position.

Power Trailer Wiring

Dennis Pottratz was instrumental in arranging donations of wiring and electrical components for the Solar Power Trailer. Bobier Electronics in West Virginia donated the Sun Selector DC Master power center. The 4000 watt sine wave inverter came from Exeltech in Texas, and the PV panels were from Brookhaven National Laboratory in New York. Most of the wiring on the trailer was done by Dennis Pottratz and Don Laughlin.

The twenty-four PV modules are wired in groups of four in series, for a system voltage of 48 volts. The six series strings are then wired in parallel in groups of two and wired to the three 50 amp PV circuit breakers in the DC control. The three sets then exit as one 48 volt system to a 100 amp mercury switch. The PVs from New York came with a large amount of very flexible 10/2 (5.3 mm square) wire with the designations SEO W-A CSA, Type STE, labeled "Polar/Solar." This wire was used between the six series strings and the three PV circuit breakers. Output from the PV array is about 20 amps at 48 volts.

The three PV circuit breakers on the face of the DC Master are rated at 50 amps DC each. The system has a 200 amp main pull-out fuse, three GFI outlets, and an AC circuit breaker box with three 20 amp fuses. An Omnimeter from Bobier Electronics measures volts, amps, and amp-hours. With all of the fuses and breakers located next to the Omnimeter, it makes troubleshooting extremely easy. The whole system, or parts of it, can be shut down easily.

During RAGBRAI, we noticed a decrease in overall current from the PV array. By using the Omnimeter and switching the three PV breakers on and off, it was very easy to isolate one subarray that was lower in output than the others. One of the PV panels in the lower middle group had developed a break in an internal connection during the trip. The bad connection did not

Mobile Photovoltaics

He Stlar hm Trailer's torn Spie«

Twenty-four PV panels provide about 20 amps at 48 volts

Three 50 Amp breakers

100 Amp mercury switch

PV shunt

Master pull-out disconnect Two 200 Amp Class-T fuses

Sixteen 6 Volt Exide lead-acid batteries 440 Amp-hours at 48 Volts

DC load shunt

Twenty-four PV panels provide about 20 amps at 48 volts

DC load shunt

Omnimeter (wiring to shunts not shown)

Three 25 Amp DC breakers

Three GFI duplex AC outlets


Omnimeter (wiring to shunts not shown)

Three GFI duplex AC outlets

Three 25 Amp DC breakers completely shut down the panel, which was replaced later.

The DC Master is connected to the PV array through the 100 amp mercury switch. When the Omnimeter senses PV voltage, the mercury switch closes. This completes the circuit to the master pull-out fuses, allowing PV current to flow to either the batteries or the inverter, or both. The schematic shows the three shunts in the DC Master—PV current, inverter current, and DC load current. These shunts allow the Omnimeter to read the different currents.

Production of Electricity

The Solar Power Trailer had already been used for similar functions around the Midwest before the RAGBRAI trip. Our experience with it at one and two day events at colleges and universities around Iowa proved it was well built and roadworthy. Last April, the PV trailer was at a two-day Earth Day event at Davis Caves in Armington, Illinois. This event included music and booths powered by our trailer. It rained constantly, but we saw that the trailer could provide as well as collect energy under adverse conditions. The battery bank started out with about 220 amp-hours available

(with a maximum 50% depth of discharge). At the end of two days, it was down to about 60 amp-hours. The voltage stayed between 49 and 46 volts.

It only rained for two of the seven days of RAGBRAI. Every day, the Omnimeter registered at least 221 amp-hours of storage in the sixteen batteries before the day's events (total battery capacity is 440 amp-hours at 48 volts). The music usually started around noon and continued throughout the afternoon and late into the evening. The PV system produced a surplus until about 5:30 in the afternoon. For about the next two hours, the production matched the power usage, and then the batteries would carry the load for the rest of the night. Reading the Omnimeter regularly showed that the musicians required at least 3,000 watts quite often during every concert. Whenever the bass guitars played, you definitely could see the wattage go even higher and the cooling fans on the inverter would turn on.

One night, the bands played until about 1:30 AM and they forgot to turn off the system when they had finished. The next morning, the amp-hours had dropped to 171. During the next day's events, we gained energy until the meter read 221 amp-hours, while still producing enough for the bands.

The Ultimate Test

Traditionally, the last night of RAGBRAI is the big event—the crowd swells to about 25,000. On that Friday night, our trailer proved how well solar-electric systems work. The bands never stopped playing and the music was loud and fast. During and after the concerts, the sound guy was constantly smiling! Later, he told me how skeptical he had been before the day's events. His comments after the concerts: "Perfect waveform, no variance in voltage during the whole day's events! No noise or pollution! A perfect 116 volts all day!" I guess a professional sound person can actually hear the effect a change in voltage makes in the music as more instruments are added. All I know is that he was impressed enough to agree to come back and help us with eighteen bands—all powered by the sun—at our seventh annual Energy Expo in September!

After the final night of the event, the Alternative Energy Tour decided one last hurrah was in order. About 35 miles into the last leg of our trip to the Mississippi River, we parked our blues music bus and Solar Power Trailer in a farmer's field next to the gravel road the bikers had to travel on. We wanted to display the PV array doing its thing out in the middle of nowhere. It was a traffic jam the rest of the afternoon. People stopped and ate and sat and listened one last time to solar-powered music.

Above: Inside the control center lives the Sun Selector DC Master power center, Omnimeter, pull-out main disconnect, and Exeltech 4KW inverter.

Final Observations

I was impressed with the way the PV panels, Exeltech Inverter, and DC Master held up. Just ask the sound guy if solar power works and is durable! This was a week of testing PV equipment under very adverse conditions. It works!

Field of Dreams was filmed here in Dyersville, Iowa. The statement from the movie, "If you build it, they will come" seems close to explaining the week of RAGBRAI. The ride was started 26 years ago. Now, people come from Australia, England, Scotland, and all over the United States. If you want to promote alternative energy, find an event like this in your area. Do It! Don't wait for "them to come" first.


Author: Tom Snyder, 611 Second St. SE, Dyersville, IA 52040 • 319-875-8772 • [email protected]

Iowa Renewable Energy Association (IRENEW), PO Box 466, North Liberty, IA 52317-0466 • 319-338-3200 [email protected]

Dennis Pottratz, Go Solar, 718 Mechanic St., Decorah, IA 52101 • 319-382-3242 [email protected]

Don Laughlin, 1881 Fox Avenue, West Branch, IA 52358 • 319-643-5650 • [email protected]

Bobier Electronics Inc., PO Box 1545, Parkersburg, WV 26102 • 304-485-6303 • Fax: 304-422-3931 [email protected]

Exeltech, 2225 East Loop 820 North, Ft Worth, TX 76118 • 800-886-4683 • 817-595-4969 Fax: 817-595-1290 • [email protected]

Jim Hurst, Brookhaven National Laboratory, Department of Applied Science, Building 179A, Upton, NY 11973 • 516-344-8000 • Fax: 516-344-4130 [email protected]

RAGBRAI, Jim Green, Des Moines Register, PO Box 622, Des Moines, IA 50303-0622 • 515-284-8282 Fax: 515-284-8138 • [email protected]

Alternative Tour Organizer: John Hazell, 1514 Mt. Pleasant St., Burlington, IA 52601 • 319-752-8689

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